I think it's too difficult for me to pick out just one favorite. I enjoyed Transformers: Dark of the Moon, Harry Potter and the Deathly Hallows, Part 2, The Grace Card, and We Bought A Zoo. Unfortunately one movie just doesn't stick out to me more than the other.
Edit: I forgot to mention Real Steel. I saw a banner at Wal*Mart this afternoon hyping the release of the DVD, January 24th. I can't wait for it!